Table of Contents

Serial Port Programming

WattmonPRO and WattmonMEGA come with an RS-232 serial interface on pins 7 and 8 and an RS-485 port on an RJ45 connector. The device is configured by default for RS-232 voltage levels and by using a simple DB9 cable can be connected to any serial device. For specific devices that require TTL levels, a jumper setting inside the device can bypass the level converter IC and it can thus be used to interface with sensors or other devices at 3.3V DC.

<?// Open the serial port at 115200 baud in non-blocking mode$fp=fseropen(115200,0);if(!$fp){print("Serial open failed");}else{$res=fwrite($fp,"Hello from wattmon");if($res){print("An error occurred while trying to write to the port");}fclose($fp);}?>

Jumper Settings Inside Wattmon

< Settings for RS-232 Mode < Settings for TTL Mode

RS-232 Cable Connection

In order to connect to a device you will need to procure a DB9 cable (male or female) and connect it up as shown in the following diagram:

Using the RS-485 Serial Port

In order to use the RS-485 port, you need to disable modbus polling. This is done from the Devices > Options > Edit Communication Settings as shown here:

<?// Open the 485 port at 115200 baud with no parity$fp=f485open(115200,0);if(!$fp){print("Serial open failed");}else{$res=fwrite($fp,"Hello from wattmon");if($res){print("An error occurred while trying to write to the port");}fclose($fp);}?>